Advances in battery technology have enabled the fabrication of tiny, high-energy-density electrochemical batteries capable of powering a wide variety of devices for extended periods of time while occupying small volumes. An electrochemical battery comprises an electrolyte interposed between two electrodes (i.e., an anode and a cathode). Electrochemical reactions between the anode and the electrolyte and between the electrolyte and the cathode cause an electrical potential to be generated between the electrodes. Continued electrochemical reactions drive an electrical current from one electrode, through a device connected to the electrodes, to the opposite electrodes, allowing various devices to be powered by the electrical current.
Lithium ion batteries, for example, include a cathode and an anode separated from one another by an electrolyte that transfers lithium ions. During discharge, when the battery is providing current to a device connected across the electrodes, redox reactions occur at the two electrodes. Oxidation reactions at the anode ionize lithium, which releases electrons to the connected circuit from the anode causing a current to flow through the connected device from cathode to anode (i.e., reverse the direction of electron travel). Lithium ions are transferred through the electrolyte from the anode to the cathode to balance the flow of electrons in the device. At the cathode, the lithium ions and electrons are reduced. The difference in energy potential between the lithium when at the anode and at the cathode corresponds to the chemically stored energy in the battery. In some cases, lithium batteries may be re-charged by applying a reverse current to the electrodes, which causes lithium ions to traverse the electrolyte in the opposite direction, and to re-supply the anode with lithium.
Some electrochemical batteries may be implemented as solid-state batteries. That is, the electrodes and electrolyte can each be solid-state films, which may be layered on top of one another to create a stacked structure disposed on a substrate. Solid-state batteries have various advantages over conventional batteries. For example, solid-state batteries typically have a higher energy density; faster charging capabilities; longer life; and lower leakage current. Further, the electrolyte in solid-state batteries are typically not flammable, unlike the organic solvents used in conventional batteries.
Various techniques and systems exist for packaging a solid-state battery. One technique involves forming a solid-state battery on a substrate and applying a polymeric sealant material over and around the solid-state battery. The polymeric sealant material may act as a moisture barrier that prevents moisture from reaching the battery and negatively affecting battery performance.
However, the above and similar approaches for sealing a solid-state battery have a number of challenges and shortcomings. One challenge arises from the fact that solid-state batteries will expand and shrink during operation. For example, solid-state batteries may expand as they are charged and shrink as they are drained. As a result, the polymeric or other sealant material encapsulating the solid-state battery may break after a small number of charge/discharge cycles.
Accordingly, there exists a need for improved systems and methods for packaging a solid-state battery, including solutions that can address the challenge associated with the expanding and shrinking of a solid-state battery during operation.